I agree Thompson, we all looked so different back then. I have photos of myself and friends in the late fifties and we were absolutely sylph-like. We were well-fed in my view, on plain, simple food, plenty of vegetables and fruit, wholesome stuff with no snacking or take-aways. Sweets were still rationed during my childhood. And of course we didn't sit down much (no TV or the Internet)!
I didn't like gym at school (I'm not in the least sporty) but no girl possessed anything resembling a sports bra. I actually wore a 'liberty bodice' as a child (!)
I must say, I think the young lassies of today look lovely in their special sports clothes doing their gym, exercise machines, yoga etc. Lycra has helped to provide supportive yet stretchy garments. Very pretty and practical.